This invention relates to a gas insulated electrical apparatus including, as an electrically insulating medium, gaseous sulfur hexafluoride (SF.sub.6) or the like, and more particularly to trap means disposed in such an apparatus to trap foreign particles floating within the apparatus to prevent the particles from sticking to the surface of electrically insulating spacers for supporting a high voltage rod-shaped electric conductor involved.
Gas insulated electrical apparatus comprise generally the high voltage rod-shaped electric conductor and the grounded metallic housing in the form of a hollow cylinder for encircling coaxially the electric conductor through a plurality of supporting structures disposed at predetermined intervals in the grounded metallic housing. A conventional supporting structure has comprised a disc-shaped electrically insulating spacer having the high voltage electric conductor horizontally disposed and fixedly extending through the center thereof to be perpendicular to the surface thereof, a grounded metallic tubular member disposed in coaxial relationship within the grounded cylindrical housing to form an annular space therebetween and having an inner cylindrical surface to which the outer peripheral edge of the electrically insulating spacer is fixedly secured, and a supporting annulus connected to the cylindrical housing to support fixedly the grounded metallic tubular member to form an annular trap space. The tubular member has been provided on the lower portion of its wall with a plurality of parallel slits running substantially perpendicularly to the longitudinal axis thereof.
Floating particles of an electrically conductive foreign matter or matters are trapped in the trap space through the slits on the grounded tubular member to be prevented from sticking to the surface of the supporting spacer thereby to decrease the dielectric strength of the apparatus. However, the trapped foreign particles tend to be accumulated and piled up on those portions of the inner wall surface of the cylindrical housing adjacent to both ends of the tubular member. Therefore, gas insulated electrical apparatus such as described above have been disadvantageous in that, upon an abnormal voltage surging to the electric conductor, the foreign particles thus accumulated are again blown out. Also, such apparatus have been disadvantageous in that the cylindrical housing is required to increase in diameter because the trap space is partly defined by the grounded metallic tubular member so that the required electrically insulating space narrows by the dimension of the annular trap space.
Accordingly, it is a general object of the present invention to eliminate the disadvantages of the prior art practice as described above.
It is an object of the present invention to provide a gas insulated electrical apparatus having an improved structure effective for preventing floating particles of a foreign matter or matters within the apparatus from sticking to the surface of electrically insulating spacers for supporting a high voltage electric conductor involved.